This invention relates to a fuel injection system for mixture compressing, externally ignited, internal combustion engines employing continuous injection into a suction tube. The invention relates, more particularly, to such a fuel injection system which contains, in sequence, a measuring member as well as an arbitrarily actuatable butterfly valve, and wherein the measuring member is displaced in accordance with air-flow rate and in opposition to a resetting force. The flowing air displaces the movable part of a valve disposed in a fuel supply line for the purpose of metering out a fuel quantity in proportion to the air quantity, the metering taking place while a constant pressure difference prevails which can, however, be changed in dependence on engine parameters.
It is the purpose of fuel injection systems of this type to create automatically a favorable fuel-air mixture for all operational conditions of the internal combustion engines to make possible a complete combustion of the fuel, and, while maintaining the highest possible performance of the internal combustion engine or the lowest possible fuel consumption, to prevent or at least to reduce sharply the creation of toxic exhaust constituents. This requires that the fuel quantity be very precisely metered out according to the requirements of each operational condition of the internal combustion engine and that the proportionality between the air and fuel quantity be changed in dependence on engine parameters such as r.p.m, load and temperature.
It is already known, in fuel injection systems of this type, to change the pressure difference at a metering valve electromagnetically, using a differential pressure valve. The constantly more stringent legal requirements for exhaust gas constituents make necessary a very precise regulation of the optimum quantity of fuel to be injected.